1. Field Of The Invention
The present invention is concerned with a self-blunting needle assembly especially suited for use in conjunction with a catheter, and with catheter assemblies including such needle assemblies. More particularly, the present invention is concerned with a needle assembly which is self-blunted prior to removal from an over-the-needle catheter implanted by use of the needle assembly.
2. Description of Related Art
A. Hypodermic Syringes Employing Locking Means Or The Like
Hypodermic syringes including locking means or the like designed to prevent reuse of the device are known. For example, U.S. Pat. No. 4,367,738 discloses a hypodermic syringe in which the plunger rod is fitted with flexible spikes which expand as the plunger is depressed in order to lock the plunger rod within the barrel portion of the syringe, thereby preventing retraction of the plunger rod for reuse of the syringe.
U.S. Pat. No. 3,478,937 discloses a syringe in which a collar unit on the plunger stem serves to prevent subsequent retraction of the plunger for reuse of the device.
U.S. Pat. No. 4,233,975 discloses a syringe in which a plug is seated by movement of the plunger rod and blocks further liquid flow to the needle mouth.
U.S. Pat. No. 4,391,273 discloses a syringe in which the plunger carries a protruding pin 67 which punctures a lower wall of the barrel in order to prevent reuse of the syringe.
U.S. Pat. No. 1,654,905 discloses a measuring syringe in which a tapering needle 9 meters the amount of discharge from the device, as explained beginning at page 1, line 72 of the patent.
B. Hypodermic Syringes With Means to Prevent Accidental Stick-Wounds
The art also shows syringes which are equipped with means intended to prevent accidental sticking of persons, such as the operator, with the needle. It is estimated that over 2,000 accidental needle-stick wounds are sustained by health care workers in the United States each day. The problem is aggravated by the trend of moving treatment out of hospitals and into doctors' offices and neighborhood clinics as part of a program to reduce health care costs. This trend increases the number and dispersion of health care workers who administer injections and draw blood samples, while reducing the frequency of such injections per individual health care worker. As a consequence, a larger number of less experienced people are administering injections and/or taking blood samples. Although in the past an occasional serious illness such as that caused by the hepatitis B virus was sustained as a result of an accidental needle-stick wound, the problem was not considered to be a serious one until the advent of the spreading of human immunodeficiency virus (HIV) infection and the knowledge that this virus is transmissible to health care workers through needle-stick wounds from a contaminated needle. The HIV causes acquired immune deficiency syndrome (AIDS), a disease which, insofar as is presently known, is invariably fatal and which has already killed tens of thousands and infected possibly millions more. HIV is often referred to simply as "the AIDS virus" and the Surgeon General of the United States of America noted in a published (September, 1987) interview that there is no better way to become infected with the AIDS virus than to take blood from an AIDS patient and accidentally inflict a needle-stick wound with the contaminated needle. This serious situation has stimulated activity to develop devices which reduce or eliminate the possibility of accidental needle-stick wounds without excessively increasing the unit cost of needles.
U.S. Pat. No. 3,890,971 discloses a single use, safety syringe which includes a plunger which is permanently lockable by detent members when the plunger has been operated to expel liquid from the barrel portion of the syringe. The disclosed structure further includes a slidable needle cap which is also permanently lockable by detent members to encase the needle within the sleeve.
U.S. Pat. No. 4,810,248 discloses a hypodermic syringe in which a combination safety sheath and needle cap is slidably mounted on the barrel to extend between a retracted position and an extended position. Means to lock the sheath in the extended position are also provided, as illustrated in the Figures of the drawing, to shield the needle to prevent inadvertent needle sticks.
U.S. Pat. No. 4,808,169 discloses a hypodermic syringe in which a double-ended hypodermic needle cannula is retained between a pair of rotatable jaws. A piston is movable through the cartridge of the syringe for expulsing the fluid contents through the needle cannula and for engaging the cannula to retrieve it irretrievably into the cartridge, to render the syringe non-reusable and protect against accidental stick wounds.
U.S. Pat. No. 4,801,295 discloses a hypodermic syringe including a sheath which is movably mounted on the syringe barrel to an extended position to cover and protect the needle. A second position of the sheath relative to the barrel and needle results in at least partially exposing the needle for use, and a third position of the sheath is employed to cover the needle with the sheath for disposal of the device. Means are provided to irreversibly lock the sheath in the third position to prevent misuse of the device.
Brochures distributed by ICU Medical Inc., of Mission Viejo, California, show a hypodermic syringe which has a sheath carried on the needle. Insofar as can be discerned from the brochure, which contains the notation "Patent Pending", the needle extends beyond the sheath for use, and the sheath is grasped by the operator upon withdrawing the needle in order to retract the needle within the sheath upon withdrawal of the needle from the patient. In this way, the sheath guards against accidental pricking of the operator with the withdrawn needle.
C. Catheter-Needle Assemblies
The use of syringe needle assemblies to insert catheters is of course well known in the art, as exemplied by U.S. Pat. No. 4,529,399. This device uses a needle member having a bore within which a catheter tube is carried, the needle being constructed to be dismantled and withdrawn to leave the catheter remaining in place, as illustrated in the drawings of the patent.
U.S. Pat. No. 4,274,408 discloses a means for inserting a catheter guide wire (12) into the vein of a patient by use of a hypodermic needle syringe. The patent discloses a locking means provided by the clip 16 (shown in FIGS. 1 and 7) which is designed to retain the guide wire 12 against any longitudinal movement relative to the syringe. After injection of the needle shaft into the vein, clip 16 is removed in order to permit withdrawal of the syringe back over the guide wire 12, as explained at column 3, lines 57-65 and column 4, lines 60-63 of the patent. The guide wire is then employed to guide a catheter 68 (FIG. 11) into the vein by means of the implanted guide wire, as explained starting at column 5, lines 4-9.